ISSN:0886-1544    

DOI:10.1002/cm.970280402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe locomotion of human polymorphonuclear leukocytes (PMNs) was studied with two complementary methods: Three‐dimensional shapes were reconstructed from time series of optical sectioning microscopy using differential interference contrast (DIC) optics, and the diffusion of cytoplasm granules within individual cells was measured using quasielastic laser light scattering (QELS). The three‐dimensional cell edges outlined in the optical sections were analyzed qualitatively in time‐lapse film strips and quantitatively from morphometry. The fastest locomotion occurred in chemotactic gradient with cell velocity that oscillated between 10 and 30 μm/min with a period of 50–55 seconds. Within the periodic bursts of speed, a fibroblast‐like locomotory cycle was observed, with leading lamella extended and contacts formed with the substrate surface, followed by rapid motion of the cell body and nucleus over the immobile contacts. Consistent with this apparent staged motion, correlation analysis revealed a phase lag of 2‐3 seconds in velocities between the bottom (ventral) and the top layers of the cell. In addition there was a tendency to a lower cell profile at times of higher velocity. The diffusion of natural cytoplasmic granules within resting PMNs was not affected by cytoskeleton disrupting drugs. During the stage of most rapid motion, when cytoplasmic streaming could be seen, diffusion of the granules decreased two‐ to 2.5‐fold, and then returned to resting levels. These observations suggest that PMN locomotion consists of extensions near the surface to form forward contacts and then stiffening or possibly contraction of the cytoskeleton when the body of the cell is moved forward.Three‐dimensional movies of PMN cells are included in the video supplement. © 1

ISSN:0886-1544    

DOI:10.1002/cm.970280403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractCytochalasin D and dBcAMP cause cultured astrocytes to change from flat cells to retrated process‐bearing cells. F‐actin was present throughout cells stimulated with dBcAMP for 16 h, whereas cytochalasin D caused F‐actin to form massive aggregates at the tips of the cell processes. The two drugs differently regulated the expression of both β‐actin and tropomyosin genes in astrocytes cultured in the presence or absence of serum: dBcAMP caused down‐regulation and cytochalasin D caused up‐regulation. Northern blot analyses indicated that: (1) serum deprivation halved the concentration of all tropomyosin transcripts (TM‐1, TM‐2, TM‐4, TMBr‐1, TMBr‐2). Serum induced TM‐4 via transcriptional activation, independent of protein synthesis, (2) dBcAMP induced down‐regulation of β‐actin (–50%) and tropomyosin transcripts (–35 to 52%) even in the presence of serum. The concentration of profilin mRNA decreased in dBcAMP‐reactive astrocytes (‐46%). The decrease in β‐actin mRNA concentration was not blocked by cycloheximide, whereas down‐regulation of tropomyosin transcripts was completely reversed when protein synthesis was inhibited, and (3) cytochalasin D induced an increase in the concentration of tropomyosin transcripts (+ 69 to 185%) which was cumulative with serum stimulation. Cytochalasin D induction of both β‐actin and TM‐4 operated through transcriptional activation, independent of protein synthesis.The production of all tropomyosin transcripts examined here were strictly coordinated with β‐actin expression in serum‐, dBcAMP‐ and cytochalasin D‐treated astrocytes. This indicates that the differential expression of tropomyosin isoforms occurring during astrocyte maturation is due to more complex regulation than that involved in seru

ISSN:0886-1544    

DOI:10.1002/cm.970280404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have investigated the effects of the microtubule poison rhazinilam on microtubule assembly in vivo and in vitro. In mammalian cells, rhazinilam mimics the effects of taxol and leads to microtubule bundles, multiple asters, and microtubule cold stability. In vitro, rhazinilam protected preassembled microtubules from cold‐induced disassembly, but not from calcium ion‐induced disassembly. Moreover, both at 0°C and at 37°C, rhazinilam induced the formation of anomalous tubulin assemblies (spirals). This process was prevented by maytansine and vinblastine, but not by colchicine. Preferential saturable and stoichiometric binding of radioactive rhazinilam to tubulin in spirals was observed with a dissociation constant of 5 μM. This binding was abolished in the presence of vinblastine and maytansine. In contrast, specific binding of radioactive rhazinilam to tubulin assembled in microtubules was undetectable. These results demonstrate that rhazinilam alters microtubule stability differently than taxol, and that the overall similar effects of rhazinilam and taxol on the cellular cytoskeleton are the consequence of two distinct mechanisms of action at the molecular level. © 1994 Wiley‐

ISSN:0886-1544    

DOI:10.1002/cm.970280405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe dynamic instability of microtubules free of microtubule‐associated proteins from two genera of cold‐living fishes was measured, by means of video‐enhanced differential interference‐contrast microscopy, at temperatures near those of their habitats. Brain microtubules were isolated from the boreal Atlantic cod (Gadus morhua;habitat temperature ∽ 2–15°C) and from two austral Antarctic rockcods (Notothenia gibberifronsandN. coriiceps neglecta;habitat temperature ∽ −1.8 to + 2°C). Critical concentrations for polymerization of the fish tubulins were in the neighborhood of 1 mg/ml, consistent with high interdimer affinities. Rates of elongation and frequencies of growth‐to‐shortening transitions (“catastrophes”) for fish microtubules were significantly smaller than those for mammalian microtubules. Slow dynamics is therefore an intrinsic property of these fish tubulins, presumably reflecting their adaptation to low temperatures. Two‐dimensional electrophoresis showed striking differences between the isoform compositions of the cod and the rockcod tubulins, which suggests that the cold‐adapted microtubule phenotypes of northern and southern fishes may have arisen independ

ISSN:0886-1544    

DOI:10.1002/cm.970280406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the present work we measured in real time the metachronism and degree of correlation between beating cilia from cultured mucociliary epithelium. The method is based on simultaneous measurement of ciliary beat frequency, phase shifts, and correlation factors in two directions: parallel and perpendicular to the effective stroke direction (ESD). From the phase shifts the lengths of wave components, and consequently the metachronal wavelength and direction, were evaluated.On active ciliary areas of cultured frog esophagus under normal conditions, a relatively high degree of correlation is observed, but cilia are more correlated in direction parallel to ESD which is also the direction of the mucus propulsion. The length of the wave component parallel to ESD is more than twice as large as that of the perpendicular component. The metachronal wavelength was found to be in the range of 5–9 μm, and the direction of the wave propagation was in the range of 90°–125° clockwise to the ESD.When ciliary beat frequency was rapidly increased by extracellular ATP or acetylcholine, only minor effects were observed on the degree of correlation between beating cilia. The length of the wave component parallel to ESD showed the most dramatic effect increasing up to tenfold. The perpendicular to ESD component was not affected by the stimulation. Consequently, the metachronism became more laeoplectic with the angle between the ESD and the wave directions decreasing by 10°–30°, and the metachronal wavelength remained unaltered. © 1994 Wile

ISSN:0886-1544    

DOI:10.1002/cm.970280407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractListeria monocytogenescan penetrate and multiply within a variety of cell types, including the PtK2kidney epithelial line. Once released within the cytoplasm,L. monocytogenesacquires the capacity for rapid movement through the host cell [Dabiri et al., 1990:Proc. Natl. Acad. Sci.87:6068‐6072]. In the process, actin monomers are inserted in proximity to one end of the bacterium, forming a column or tail of actin filaments [Sanger et al., 1992:Infect. Immun.60:3609‐3619]. The rate of new actin filament growth correlates closely with the speed of bacterial migration. In this study we have used fluorescently labeled actin and alpha‐actinin to monitor the movement and turnover rate of actin and alpha‐actinin molecules in the tails. The half‐lives of the actin and alpha‐actinin present in the tails are approximately the same: actin, 58.7 sec; alpha‐actinin, 55.3 sec. The half‐life of alpha‐actinin surrounding a dividing bacterium was 30 sec, whereas its half‐life in the tails that formed behind the two daughter cells was about 20‐30% longer. We discovered that the speeds of the bacteria are not constant, but show aperiodic episodes of decreased and increased speeds. There is a fluctuation also in the intensities of the fluorescent probes at the bacterium/tail interface, implying that there is a fluctuation in the number of actin filaments forming there. There was no strong correlation, however, between these fluctuating intensities and changes in speed of the bacteria. These measurements suggest that while actin polymerization at the bacterial surface is coupled to the movement of the bacterium, the periodic changes in intracellular motility are not a simple function of the number of actin filaments nucleating at the bacterial surfaces.

ISSN:0886-1544    

DOI:10.1002/cm.970280408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0886-1544    

DOI:10.1002/cm.970280409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0886-1544    

DOI:10.1002/cm.970280410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0886-1544    

DOI:10.1002/cm.970280401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY